1. Field of the Invention
This invention relates to the manufacture of paper and cardboard using recycled fibers
2. Background of the Prior Art
Increasingly, the papermaking industry calls for raw materials based on recycled fibers. With each recycling, the quality of the raw materials deteriorates and, in order to achieve a satisfactory level in the mechanical characteristics of the paper or cardboard produced, it is generally necessary to carry out a refinement on the papermaking pulp.
The repercussions of these effects on the formations of sheets and the yield of the papermaking machine are important. In particular, there is observed a decrease in the capability of water to drain through the fibrous layer on repeated recycling.
It is then necessary to increase the concentration of the fibrous suspensions in order to retain a rate of manufacture which is comparable to the manufacture of sheets based on natural or bleached fibers, for example.